/**
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.snbc.format;

import java.io.IOException;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.SQLException;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.classification.InterfaceStability;
import org.apache.hadoop.mapreduce.Job;
import org.apache.hadoop.mapreduce.JobContext;
import org.apache.hadoop.mapreduce.OutputCommitter;
import org.apache.hadoop.mapreduce.OutputFormat;
import org.apache.hadoop.mapreduce.RecordWriter;
import org.apache.hadoop.mapreduce.TaskAttemptContext;
import org.apache.hadoop.mapreduce.lib.db.DBConfiguration;
import org.apache.hadoop.mapreduce.lib.db.DBWritable;
import org.apache.hadoop.mapreduce.lib.output.FileOutputCommitter;
import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;
import org.apache.hadoop.util.StringUtils;

/**
 * A OutputFormat that sends the reduce output to a SQL table.
 * <p>
 * {@link MyDBOutputFormat} accepts &lt;key,value&gt; pairs, where
 * key has a type extending DBWritable. Returned {@link RecordWriter}
 * writes <b>only the key</b> to the database with a batch SQL query.
 *
 */
@InterfaceAudience.Public
@InterfaceStability.Stable
public class MyDBOutputFormat<K  extends DBWritable, V>
        extends OutputFormat<K,V> {

    private static final Log LOG = LogFactory.getLog(MyDBOutputFormat.class);
    public void checkOutputSpecs(JobContext context) {}

    public OutputCommitter getOutputCommitter(TaskAttemptContext context)
            throws IOException {
        return new FileOutputCommitter(FileOutputFormat.getOutputPath(context),
                context);
    }

    /**
     * A RecordWriter that writes the reduce output to a SQL table
     */
    @InterfaceStability.Evolving
    public class DBRecordWriter
            extends RecordWriter<K, V> {

        private Connection connection;
        private PreparedStatement statement;

        public DBRecordWriter(Connection connection
                , PreparedStatement statement) throws SQLException {
            this.connection = connection;
            this.statement = statement;
            this.connection.setAutoCommit(false);
        }

        public Connection getConnection() {
            return connection;
        }

        public PreparedStatement getStatement() {
            return statement;
        }

        /** {@inheritDoc} */
        public void close(TaskAttemptContext context) throws IOException {
            try {
                statement.executeBatch();
                connection.commit();
            } catch (SQLException e) {
                try {
                    connection.rollback();
                }
                catch (SQLException ex) {
                    LOG.warn(StringUtils.stringifyException(ex));
                }
                LOG.error("---------------------"+statement);
                throw new IOException(e);
            } finally {
                try {
                    statement.close();
                    connection.close();
                }
                catch (SQLException ex) {
                    throw new IOException(ex.getMessage());
                }
            }
        }

        /** {@inheritDoc} */
        public void write(K key, V value) throws IOException {
            try {
                key.write(statement);
                statement.addBatch();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
    }

    /**
     * Constructs the query used as the prepared statement to insert data.
     *
     * @param table
     *          the table to insert into
     * @param fieldNames
     *          the fields to insert into. If field names are unknown, supply an
     *          array of nulls.
     */
    public String constructQuery(String table, String[] fieldNames) {
        if(fieldNames == null) {
            throw new IllegalArgumentException("Field names may not be null");
        }

        StringBuilder query = new StringBuilder();
        query.append("INSERT INTO ").append(table);

        if (fieldNames.length > 0 && fieldNames[0] != null) {
            query.append(" (");
            for (int i = 0; i < fieldNames.length; i++) {
                query.append(fieldNames[i]);
                if (i != fieldNames.length - 1) {
                    query.append(",");
                }
            }
            query.append(")");
        }
        query.append(" VALUES (");

        for (int i = 0; i < fieldNames.length; i++) {
            query.append("?");
            if(i != fieldNames.length - 1) {
                query.append(",");
            }
        }
        //query.append(");");
        query.append(")");

        return query.toString();
    }

    /** {@inheritDoc} */
    public RecordWriter<K, V> getRecordWriter(TaskAttemptContext context)
            throws IOException {
        DBConfiguration dbConf = new DBConfiguration(context.getConfiguration());
        String tableName = dbConf.getOutputTableName();
        String[] fieldNames = dbConf.getOutputFieldNames();

        if(fieldNames == null) {
            fieldNames = new String[dbConf.getOutputFieldCount()];
        }

        try {
            Connection connection = dbConf.getConnection();

            PreparedStatement statement = null;
            String sql=constructQuery(tableName, fieldNames);
            LOG.info("======================>"+sql);
            statement = connection.prepareStatement(sql);
            return new DBRecordWriter(connection, statement);
        } catch (Exception ex) {
//
            LOG.error(ex.getMessage(),ex);
            throw new IOException(ex.getMessage());
        }
    }

    /**
     * Initializes the reduce-part of the job with
     * the appropriate output settings
     *
     * @param job The job
     * @param tableName The table to insert data into
     * @param fieldNames The field names in the table.
     */
    public static void setOutput(Job job, String tableName,
                                 String... fieldNames) throws IOException {
        if(fieldNames.length > 0 && fieldNames[0] != null) {
            DBConfiguration dbConf = setOutput(job, tableName);
            dbConf.setOutputFieldNames(fieldNames);
        } else {
            if (fieldNames.length > 0) {
                setOutput(job, tableName, fieldNames.length);
            }
            else {
                throw new IllegalArgumentException(
                        "Field names must be greater than 0");
            }
        }
    }

    /**
     * Initializes the reduce-part of the job
     * with the appropriate output settings
     *
     * @param job The job
     * @param tableName The table to insert data into
     * @param fieldCount the number of fields in the table.
     */
    public static void setOutput(Job job, String tableName,
                                 int fieldCount) throws IOException {
        DBConfiguration dbConf = setOutput(job, tableName);
        dbConf.setOutputFieldCount(fieldCount);
    }

    private static DBConfiguration setOutput(Job job,
                                             String tableName) throws IOException {
        job.setOutputFormatClass(MyDBOutputFormat.class);
        job.setReduceSpeculativeExecution(false);

        DBConfiguration dbConf = new DBConfiguration(job.getConfiguration());

        dbConf.setOutputTableName(tableName);
        return dbConf;
    }
}
